The present invention relates to an improved inner cable. More particularly, the present invention relates to the inner cable which can be operated by push-pull operation without generating a noise.
The inner cable is essentially formed by spirally winding at least one metal wire having a comparatively large diameter on the outer surface of a core comprising a metal strand at the same intervals to make teeth. The teeth of the inner cable are meshed with the other gear or the other similar inner cable (hereinafter referred to as an engagement element) to rotate the engagement element by the movement of the inner cable or to move the inner cable by the rotation of the engagement element.
Such an inner cable usually is flexible, and is inserted into a conduit to use as a control cable for the remote control of various industrial mechanisms. A flexible tube being a metal spiral tube or a non-flexible tube merely being a metal tube is used as a conduit, and is usually bent between the operating side and the working side.
When the inner cable is operated within such a conduit, the teeth of the inner cable are slidably contacted to the inner surface of the conduit made of metal. Especially, in the case that the conduit is bent, the above teeth discontinuously contact the inner surface of the conduit, and then generate the noise.
Also, the control cable comprising the inner cable and the conduit is often applied to, for example, shut and open of a sun roof, a window glass or the like in an automobile. In a cabin of the automobile, the noise makes a driver and passengers uncomfortable, even if that is small.
Since the noise generated by the frequent contact of the geared cable and the conduit due to the oscillation or vibration of the automobile is also included in the noise generated in the automobile, it is eagerly desired to prevent the noise generated in the control cable comprising the inner cable and the conduit.
In order to prevent the noise in such a control cable, it has been suggested that an inner tube made of synthetic resin is interposed between the inner cable and the conduit. However, there is drawback that the control cable produced is insufficient in preventing the noise, because the noise is generated by the slidable contact of the inner tube and the inner cable.
Also, it has been suggested that a brush-like layer comprising short fibers and having spring function is bonded to the outer surface of the core in the inner cable or the inner surface of the conduit (Japanese Patent Publication No. 5041/1969). However, the brush-like layer wears after a comparatively short term in use, and the noise is generated. In addition, the control cable suggested has the drawback that the function of the inner cable is prevented, because the short fibers come out from the bonded surface, and are stuffed between the geared cable and the conduit.
Furthermore, it has been suggested that an elastic foamed layer made of synthetic resin such as polyurethane is provided on the outer surface of the core between adjacent teeth, so that a top of that is projected outwardly more than those of the teeth (U.S. Ser. No. 63,402). Accordingly, the foamed layer is directly contacted with the conduit without the teeth being not contacted with the conduit, and therefore the noise can be effectively prevented. When the geared cable is meshed with the engagement element, the foamed layer is depressed by the tooth of the engagement element. In that case, there is drawback that the foamed layer is sandwiched between the tooth of the geared cable and that of the engagement element, and as a result, is torn off.